In recent electric equipment such as vacuum cleaners requiring electrically powered blowers, electric supply to a motor section comprising a stator and a rotor is controlled by a drive circuit in many cases.
In the electrically powered blower used in such equipment, since driving current is increased as blowing ability is increased, a heating value of a power element used in the drive circuit is increased, and a heat radiation plate made of aluminum is mounted on the power element to suppress the temperature rise of the element.
A conventional electrically powered blower has a structure as shown in FIG. 11.
A motor section A has a motor casing B including a pair of brackets 3 and 4. A stator 1 and a rotor 2 are incorporated in the motor casing B. An output shaft 5 rotatably supports the rotor 2, and extends outside of the motor casing B. A rotation fan 6 is mounted on a tip end of the output shaft 5. An air guide 7 is mounted such as to divide the rotation fan 6 from the stator 1 and the rotor 2. A fan case 8 is mounted such as to cover the rotation fan 6 and the air guide 7. The fan case 8 has an opening corresponding to a suction port 12 of the rotation fan 6. An air passage C is formed such that air in a discharge port 13 of the rotation fan 6 is discharged from an inner side of the motor casing B.
A drive circuit 9 controls electric supply to the motor section A. The drive circuit 9 is mounted on a heat radiator 11 which is disposed in the vicinity of the motor casing B. Heat of power elements 10 of the drive circuit 9 is radiated to the heat radiator 11. The heat radiator 11 comes into contact with air flow which is discharged from a discharge port 14 formed in the bracket 4, and is forcibly cooled, so that the temperature rise is suppressed.
More specifically, when the motor section A is a three-phase brushless motor, a plurality of power elements 10 which control the electric supply to the phases are mounted on the heat radiator 11.
In the electric equipment having the above-described electrically powered blower, in order to efficiently cool the drive circuit 9 and the power elements 10, it is common to increase the air amount of the air flow which comes into contact with the heat radiator 11 and passes therethrough, or to increase the size of the fins themselves of the heat radiator 11.
However, if the air amount of the air flow which comes into contact with the heat radiator 11 and passes therethrough is increased, the air amount flowing to the stator 1 and the rotor 2 of the motor section A is reduced, so that the motor section A can not be cooled sufficiently. If the size of the fins themselves of the heat radiator 11 are increased, there is a problem that the size of the electric equipment itself is increased.